Regulating Porous Structure of Dual-Percolation Polybutene-1 (PB)/Poly(ethylene-co-octene) (POE)/Carbon Nanotube (CNT) Composites for Enhanced Electrical Conductivity and Electromagnetic Interference Shielding Performance

The dual-percolation polybutene-1 (PB)/poly(ethylene-co-octene) (POE)/carbon nanotube (CNT) composite foams with lightweight, high conductivity, and high-efficiency EMI shielding performance were successfully prepared via melt blending followed by supercritical carbon dioxide (sc-CO2) foaming. The CNTs' selective location in the PB phase of PB/POE/CNT composites was verified based on the kinetic/thermodynamic predictions and scanning electron microscopy observations. The dual percolation structure and porous microstructure of composites affecting the electrical conductivity and EMI shielding property were carefully evaluated. Owning to the bimodal porous structure of dual-percolation composite foams, in which large pores contributed to increasing porosity and small pores dedicated to maintaining the connectivity in conductive networks, the high void fraction and high conductivity were simultaneously achieved. The electromagnetic interference (EMI) shielding performance showed that the foamed PB/POE/CNT composites with 1.4 vol % CNTs loading displayed a 71% decrease in density, 43.2% increase in absorptivity, 41.1% increase in EMI shielding effectiveness (SE), and 76.4% increase in specific EMI SE, in comparation with the solid PB/POE/CNTs loaded with 1.6 vol % CNTs. Moreover, the foamed PB/POE/CNT composites with a 3.3 vol % CNT loading achieved a high EMI SE of 22.4 dB, satisfying the requirements of commercial EMI shielding materials (≥20 dB).